1. ABL-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, MD 21701.
2. National Institute of Allergy and Infectious Diseases, Laboratory of Molecular Microbiology, Bethesda, MD 20892.
3. Lederle Laboratory, Pearl River, NY 10965.
4. Mammalian Cell Genetics, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724.